4 ms·
The force curve precluded single-certification without MCAS, but I haven't seen any claim that it would not be certified at all. 'Stable' is the critical term,
by Obi_Juan_Kenobi 6y ago
The force curve precluded single-certification without MCAS, but I haven't seen any claim that it would not be certified at all. 'Stable' is the critical term, and is loosely defined.
In reality, the force curves always deviate from the ideal, save in fly-by-wire designs. There are two different issues at play:
The first is a force curve that deviates so much that it becomes unintuitive or unmanageable to fly. This would not be acceptable, but I have not seen someone claim the 737 MAX would be characterized this way.
The second is whether the force curves of the older 737s matched the MAX closely enough. These pilots are expecting a certain behavior, and under single certification, could be going back and forth between these models often. Even small differences in handling between these could be jarring and lead to bad stick inputs.
This is a much more demanding requirement because of the context; in the first case, a pilot is making one transition to a new aircraft that they expect will be different from what they flew before. In the second, they are switching between aircraft often, perhaps after long stretches of becoming accustomed to one model or the other. They must then constantly be aware of these differences and continually adjust for them, a situation ripe for error.
My understanding is that the 737Max flies kinda like a 757 without MCAS. It's not a big deal.
- FabHK 6y agoInsightful clarification. It is hard to find reliable sources on this, I must say. I base my conclusion for example on these excerpts from [1]: > MCAS would trigger in narrow circumstances. It was designed “to address potentially unacceptable nose-up pitching moment at high angles of attack at high airspeeds,” Boeing told the FAA in a proprietary System Safety Assessment (This doesn't specify whether it would be unacceptable for certification, or for certification under the same type certificate.) > Engineers determined that on the MAX, the force the pilots feel in the control column as they execute this maneuver would not smoothly and continuously increase. Pilots who pull back forcefully on the column — sometimes called the stick — might suddenly feel a slackening of resistance. An FAA rule requires that the plane handle with smoothly changing stick forces. (This seems to indicate that it would be unacceptable under the general FAA rule.) [1] https://www.seattletimes.com/seattle-news/times-watchdog/the-inside-story-of-mcas-how-boeings-737-max-system-gained-power-and-lost-safeguards/ https://www.seattletimes.com/seattle-news/times-watchdog/the...
- slavak 6y agohttps://aviation.stackexchange.com/questions/73132/did-boeing-need-mcas-because-the-737-max-didn-t-meet-faa-longitudinal-stability https://aviation.stackexchange.com/questions/73132/did-boein...